Wearable Sensors: Recyclable Nonfunctionalized Paper‐Based Ultralow‐Cost Wearable Health Monitoring System (Adv. Mater. Technol. 4/2017)

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For decades, the revolution in design and fabrication methodology of flexible capacitive pressure sensors using various inorganic/organic materials has significantly enhanced the field of flexible and wearable electronics with a wide range of applications in aerospace, automobiles, marine environment, robotics, healthcare, and consumer/portable electronics. Mathematical modelling, finite element simulations, and unique fabrication strategies are utilized to fabricate diverse shapes of diaphragms, shells, and cantilevers which function in normal, touch, or double touch modes, operation principles inspired from microelectromechanical systems (MEMS) based capacitive pressure sensing techniques. The capacitive pressure sensing technique detects changes in capacitance due to the deformation/deflection of a pressure sensitive mechanical element that alters the separation gap of the capacitor. Due to advancement in state‐of‐the‐art fabrication technologies, the performance and properties of capacitive pressure sensors are enhanced. In this review paper, recent progress in flexible capacitive pressure sensing techniques in terms of design, materials, and fabrication strategies is reported. The mechanics and fabrication steps of paper‐based low‐cost MEMS/flexible devices are also broadly reported. Lastly, the applications of flexible capacitive pressure sensors, challenges, and future perspectives are discussed.

Section: Discussion On Various Design Approaches With Advantages and mentioning

confidence: 99%

Section: Electrodes For Flexible Capacitive Pressure Sensorsmentioning

confidence: 99%

Recent Progress on Flexible Capacitive Pressure Sensors: From Design and Materials to Applications

Mishra

El‐Atab

Hussain

et al. 2021

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“…With the increasing demands of flexible devices, flexible sensors have attracted extensive attention due to their wide applications in soft robots, [ 1 ] physiological monitoring, [ 2 ] and wearable devices. [ 3 ] Among them, soft strain sensors can detect the movement of hands and limbs, [ 4 ] blood pulse, [ 5 ] and respiration rate, [ 6 ] indicating the vital signs of the human body. These sensors work with different sensing mechanisms [ 7 ] e.g., piezo‐resistivity, [ 4b ] capacitance, [ 8 ] and piezo‐electricity [ 9 ] would transduce the strain, pressure, force and vibration into electrical signal.…”

Section: Introductionmentioning

confidence: 99%

Highly Filled Glycerol/Graphite Suspensions as Fluidic Soft Sensors and Their Responsive Mechanism to Shear

Zhou

Guo

2020

The conductive suspensions composed of high content of graphite flakes dispersed in glycerol demonstrate flow field sensitive resistance and memory effect of the deformation history, which are expected to work as new fluidic soft sensors. The resistance of the suspensions responds to the local flow field caused by vibrations, stretching, and shear. The combined electro‐rheo tests are carried out to reveal the resistance response to different types of flow field. Based on the variations of resistance, a microstructural model considering the direction of the flow field and the corresponding transition kinetics of the different microstructures of fillers are established in the present work. The contents of the microstructures vary with both the shear strain and the shear direction and the transition rate between the different microstructures depended on the shear rate. The unveiled mechanism via the proposed model is expected to deepen the understanding of conductive suspensions so as to further guide the design of soft sensors based on conductive suspensions and composites.

“…Papertronics (paper‐based electronics) have recently emerged as a next‐generation “green” electronic platform with the goal of tackling deformability, cost‐effectiveness, electronic waste management, environmental pollutions, and resource shortages . Papertronics possess unique characteristics including foldability/flexibility/light weight, low cost, biodegradability/renewability, eco‐friendliness, and probability for abundance .…”

Section: Introductionmentioning

confidence: 99%

Merging Electric Bacteria with Paper

Gao

Choi

2018

other electronic components. [18,19] Revolutionary combinations of synthetic materials and paper allow the development of unconventional electronics, which cannot be built with traditional semiconductor technology. While the combinations are revolutionary, these materials can be blended with paper by using mature manufacturing processes, such as roll-to-roll printing, soaking, coating, screen-printing, and dipping. [8,12,[20][21][22] Many functional inks, [23] synthetic polymers, [24] metals, [25] semiconductors, [26] insulators, [27] and nanoparticles [28] have integrated into the paper. The combinations can make paper conductive, biocompatible, biodegradable, smooth, and protective by filling the pores, covering the fibers, and laminating the surface. [6,29,30] Other biological materials such as enzymes, proteins, and DNAs, have also been used to functionalize the paper. [31][32][33] Recently, electric bacteria (exoelectrogens) that are capable of harvesting electrons have been innovatively merged with paper to power on-chip paper devices (Figure 1). [34][35][36] These electric bacteria use respiration to convert biochemical energy stored in organic matter into biological energy, adenosine triphosphate (ATP), where this process involves a cascade of reactions through a system of electron-carrier biomolecules in which electrons are transferred to the terminal electron acceptor, an anode. [37] During the bacterial respiration, protons are also generated, which diffuse through a selective ion exchange membrane and reach a cathode. Those electrons and protons are reduced to water in the presence of catholyte (e.g., oxygen) at the cathode. Paper-based batteries or energy storage devices have been considered as an indispensable component in creating selfsustainable and independent papertronics. [38][39][40] Paper-based solar cells, [41] supercapacitors, [28] nanogenerators, [42] thermoelectrics, [21] and chemical fuel cells [43] have been widely studied as potential energy sources in various applications. Incorporating electric bacteria into paper can offer a simple but powerful energy source for papertronics especially in remote and resource-limited settings as the bacteria can inhabit any environment even those with extreme conditions. [44] Furthermore, the device can be compact, affordable, and easily integrated into a simple structure's design in a cost-effective and eco-friendly manner. The paper's high roughness and porosity can be advantageous for bacterial accommodation and mass transfer relative to the bacterial energy harvesting while its hydrophilicity easily absorbs bacterial media and holds it for Paper-based electronics (papertronics) are recently considered as one of the most exciting device platforms because of their flexibility, sustainability, ecofriendliness, and low cost as well as their excellent mechanical, dielectrical, and fluidic properties. Now, innovative structure engineering techniques can manipulate diameters of the cellulose fibers of paper, smoothing the roughness and controlling the t...